The invention relates to the further development of certain surgical instruments like those used especially in the area of minimal invasive surgery. These instruments are generally introduced into the interior of the body with the aid of an endoscope and used primarily for diagnostic purposes. One disadvantage of the purely mechanically functioning "tools" of the physician (for example the probe and forceps) is that they do not offer a sense of touch adequate for the surgeon's hand, with whose aid the physician obtains important information during open surgery.
A number of studies are already known with regard to "tactile sensing" which relate mainly to applications in robotics. S. Omata et al., "New tactile sensor like the human hand and its applications," Sensors and Actuators A, 35 (1992) 9.15, describe a tactile sensor based on a piezoelectric oscillator (PZT) to determine the hardness or softness of tissues "quite similarly to the human hand".
K. Suzuki et al., A 1024-Element High-Performance Silicon Tactile Imager," IEEE Trans. El. Dev. 37, 1990, 1852-1860 developed a high-resolution "tactile imager" composed of 1024 (32.times.32) capacitive pressure sensors for precision robotics.
As the basic component, S. Sugiyama et al., "Tactile Image Detection Using a k-Element Silicon Pressure Sensor Array," Sensors and Actuators A, 2123 (1990), 397-400 describe a pressure sensor array likewise with 32.times.32 elements.
A device related to the medical field is described in German Patent Document DE-OS 42 13 584. In this so-called "object information modeling device" (diagnostic device) in the first embodiment which is relevant here, an endoscope device is described for optical (i.e. zero contact) object acquisition. By means of stereo CCD optics, the data for generating a 3 D image on a monitor are collected. This height profile can be selected pointwise with a mouse. An actuator integrated into the mouse, in the form of a bending rod (driven by piezo or SMA elements) is adjusted as a function of the relative height of the object point and can be felt with the finger. Hence the diagnosis is limited to pure modeling of "unevenness" or "degree of swelling" of the object under investigation. Of course its elastic properties (hardness) cannot be determined. In another embodiment of German Patent Document DE-OS 42 13 584, detection of object temperature using IR sensing is proposed as well.
In the present invention, an actuator array made of so-called "ERF cells" is used as the key element for the desired modeling of the sense of touch. These are control elements that contain an electrorheologic fluid (ERF) as an active medium.
ERF actuators have been described in the past in the form of couplings, shock absorbers (active damping system), valves, and pumps.
In contrast to the highly complex diagnostic system described in German Patent Document DE 42 13 584 A1, the goal of the present invention is to implement the functions of (i) detection of object properties that can be determined by feel, and (ii) direct modeling of these properties in a manner that can be felt, within a single endoscopic instrument. This instrument can be desinged either as a so-called probe or as forceps.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.